The purpose of this study is to help determine the functional role of the arcuate nucleus of the hypothalamus in reproductive neuroendocrine mechanisms. The experiments outlined in this proposal will 1) focus on the role of the arcuate nucleus and preoptic area in steroid feedback mechanisms in the male & female animal, 2) study the role of these hypothalamic structures in the induction of LH surges and 3) study the role of dopamine in the control of gonadotropin secretion. The animal model to be used in this study will be the hamster which was treated neonatally with monosodium glutamate. On the basis of preliminary studies this type of treatment results in a specific lesion of the arcuate nucleus. Some of the techniques and procedures to be used on animals with this lesion include: hormone replacement therapy, hypothalamic deafferentation, electrochemical stimulation of the hypothalamus, measurement of plasma and pituitary gonadotropins and gonadal steroids by radio-immunoassay and fluorescence and enzyme histochemistry.